Date of Award

December 2019

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Civil and Environmental Engineering


Riyad Aboutaha


Bridge widening, CFRP, experimental test, Finite element modeling

Subject Categories



Increase in traffic load dictates widening highway bridges rather than construction of new bridges, as it offers an economical solution. Highway bridge widening is usually accomplished by the construction of additional new bridge piers, however, large amount of construction work and extensive use of heavy plant and machinery could result in very high cost. For limited widening of bridges, e.g. addition of one driving/emergency lane, extension of the pier cap beam offers an attractive solution. Due to additional load resulting from the widened bridge, strengthening of extended cap beams may be needed. In addition, depending on the strength of the existing pier column, limited strengthening of the column will probably be needed.

This research project presents a bridge cap beam extension and reinforcing system, which is considered an alternative of constructing new piers for bridge widening projects. Experimental results and numerical modeling of quarter-scaled reinforced concrete hammerhead non-prismatic pier cap beams, extended on verges and reinforced with different CFRP systems are presented, followed by development of a practical analytical model. In addition, a column strengthening system, which provides a continuous load path to transfer additional moment to the foundation, was presented in this study.

The experimental work was to investigate the structural performance of this particular type of beams with different reinforcing systems, such as concrete jacket, CFRP sheets and pre-saturated CFRP laminates with various anchor systems. Thirteen pier cap beam specimens were tested to evaluate the effect of the reinforcing systems on ultimate strength, stiffness and ductility. In addition, five full-scaled rectangular RC columns strengthened with either concrete jacket or vertical CFRP plates were tested under cyclic loading, flexural and cyclic performance of strengthened columns, and strain distribution on CFRP composites were investigated.

A numerical study based on finite element modeling was performed to investigate the failure mechanism of tested beams. A 3-D finite element model was developed and verified against experimental results. A good agreement between finite element results and experimental results was achieved in terms of failure mode, ultimate capacity and load-deflection response.

The experimental work and finite element results demonstrated the feasibility of proposed cap beam extension system. All of the tested reinforcing systems are effective in improving flexural strength of the extended cap beams. Among the investigated reinforcing systems, the fully wrapped CFRP sheet offers the most efficient solution for proposed system. Based on these observations, an iterative based simple practical analytical model was developed to predict the ultimate capacity of extended cap beams with CFRP reinforcing systems. A few design and construction recommendations are presented at the end of the dissertation.


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